The low surface brightness Universe holds clues to the first formation of galaxies. Specifically, the shape and morphology of local stellar haloes have encoded in them the early formation history of their parent galaxies. Early progenitor galaxies were absorbed by the dark halo and scattered their stars in a diffuse halo around the main galaxy. If the accretion event was relatively recent, it may show as a coherent stream of stars within the halo. in addition, the low-mass, low-surface brightness satellite galaxies, perhaps the ultradiffuse galaxies recently reported would help solve the "Missing Dwarf Problem", the apparent over-prediction of $Λ$CDM models of the number of satellite galaxies around a Milky Way Halo.
However low surface brightness is not what most telescopes are optimized for, most are best for resolving point sources and not sensitivity for large-scale low-light. To be sensitive to the low surface brightness Universe, a telescope needs a simple, unobstructed light path (disfavoring mirrors), fast optics (low f/D), and relatively coarse sampling (big pixels). Exceptions are the superb Dragonfly and Huntsman telescopes which are purposely designed to be sensitive to low surface brighnesses. Similarly designed, if not with low surface brightness in mind is the successfully launched TESS satellite. We show in this Research Note that the envisaged total exposure times and optical setup are near-ideal for low surface brightness work in the local Universe.
With combined TESS imaging, one can model the stellar halo surrounding a galaxy. Technical challenges include the image quality, zodiacal and Galactic cirrus background light, PSF characterization and subtraction. Once accounted for with a processing pipeline, one can model the stellar halo for all nearby galaxies and to search for substructure in these haloes.
In this paper, a total of about 28000 images in $V$ and $R$ band obtained on 161 nights using the one-meter optical telescope at Weihai Observatory (WHO) of Shandong University since 2008 to 2012 have been processed to measure the sky brightness. It provides us with an unprecedented database, which can be used to study the variation of the sky brightness with the sky position, the moonlight contribution, and the twilight sky brightness. The darkest sky brightness is about 19.0 and 18.6 $mag$ $arcsec^{-2}$ in $V$ and $R$ band, respectively. An obvious darkening trend is found at the first half …
The sky brightness is a critical parameter for estimating the coronal observation conditions for solar observatory. As part of a site-survey project in Western China, we measured the sky brightness continuously at the Lijiang Observatory in Yunnan province in 2011. A sky brightness monitor (SBM) was adopted to measure the sky brightness in a region extending from 4.5 to 7.0 apparent solar radii based on the experience of the Daniel K. Inouye Solar Tele- scope (DKIST) site survey. Every month, the data were collected manually for at least one week. We collected statistics of the sky brightness …
Tibet is known as the third pole of the earth, as high as the South Pole and North Pole. The Ngari (Ali) observatory in Tibet has the advantage of plenty of photometric night, low precipitable water vapor, high transmittance, good seeing. It is a good site, and promising to be one of the best place for infrared and submillimeter observations in the world. However, there is no data available for sky background brightness in such place, which restrict the astronomical development of the sites. In the near infrared band of J, H, Ks, a NIR sky brightness monitor (NISBM) is designed based on InGaAs…
We present optical UBVRI zenith night sky brightness measurements collected on eighteen nights during 2013--2016 and SQM measurements obtained daily over twenty months during 2014--2016 at the Observatorio Astronomico Nacional on the Sierra San Pedro Martir (OAN-SPM) in Mexico. The UBVRI data is based upon CCD images obtained with the 0.84m and 2.12m telescopes, while the SQM data is obtained with a high-sensitivity, low-cost photometer. The typical moonless night sky brightness at zenith averaged over the whole period is U = 22.68, B = 23.10, V = 21.84, R = 21.04, I = 19.36, and SQM = 21.88 m…
We report studies on the mitigation of optical effects of bright low-Earth-orbit (LEO) satellites on Vera C. Rubin Observatory and its Legacy Survey of Space and Time (LSST). These include options for pointing the telescope to avoid satellites, laboratory investigations of bright trails on the Rubin Observatory LSST camera sensors, algorithms for correcting image artifacts caused by bright trails, experiments on darkening SpaceX Starlink satellites, and ground-based follow-up observations. The original Starlink v0.9 satellites are g ~ 4.5 mag, and the initial experiment "DarkSat" is g ~ 6.1 ma…
We present night sky brightness measurements performed at the Vienna University Observatory and at the Leopold-Figl-Observatorium fuer Astrophysik, which is located about 35km to the southwest of Vienna. The measurements have been performed with Sky Quality Meters made by Unihedron. They cover a time span of roughly one year and have been carried out every night, yielding a night sky brightness value every 7 seconds and thus delivering a large amount of data. In this paper, the level of light pollution at the Vienna University Observatory, which ranges from 15 to 19.25 magnitudes per square ar…
We present spectroscopic measurements on the night sky of Xinglong Observatory for a period of 12 years from 2004 to 2015. The spectra were obtained on moonless clear nights using the OMR spectrograph mounted on a 2.16-m reflector with a wavelength coverage of 4000-7000A. The night sky spectrum shows the presence of emission lines from Hg I and Na I due to local artificial sources, along with the atmospheric emission lines, i.e., O I and OH molecules, indicating the existence of light pollution. We have monitored the night sky brightness during the whole night and found some decrement in the s…
We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial satellite constellations in low-Earth orbit on the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate the orbits of currently planned Starlink and OneWeb constellations ($\sim$40,000 satellites) to test how effectively an upgraded Rubin scheduler algorithm can avoid them, and assess how the overall survey is affected. Given a reasonably accurate satellite orbit forecast, we find it is possible to adjust the scheduler algorithm to effectively avoid some satellites. Overall, …
A new astronomical observatory in southeastern Indonesia is currently under construction. This Timau National Observatory will host a 3.8-metre telescope for optical and near-infrared observations. To support the operation and planning, the characterisation of the site needs to be appropriately performed. However, limited resources and access to the site hindered the deployment of instruments for comprehensive site testing. Fortunately, \emph{in-situ} sky brightness data from the Sky Quality Meter (SQM) have been available for almost two years. Based on the data acquired in 470 nights, we obta…
A model that combines celestial geometry and atmospheric physics is used to calculate the dimming of artificial satellites as they enter and exit the Earth's shadow. Refraction of sunlight by the terrestrial atmosphere can illuminate a satellite while it is inside the eclipse region determined from geometry alone. Meanwhile, refraction combines with atmospheric absorption to dim the satellites for tens of km outside of that region. Spacecraft brightness is reduced more in blue light than in red because absorption of sunlight is stronger at shorter wavelengths. Observations from the MMT-9 robot…
The main features of SG-WAS (SkyGlow Wireless Autonomous Sensor), a low-cost device for measuring Night Sky Brightness (NSB), are presented. SG-WAS is based on the TSL237 sensor --like the Unihedron Sky Quality Meter (SQM) or the STARS4ALL Telescope Encoder and Sky Sensor (TESS)--, with wireless communication (LoRa, WiFi, or LTE-M) and solar-powered rechargeable batteries. Field tests have been performed on its autonomy, proving that it can go up to 20 days without direct solar irradiance and remain hibernating after that for at least \mbox{4 months}, returning to operation once re-illuminated…
In this draft photometry and astrometry is presented from the Herschel Space Observatory (HSO). This spacecraft orbits the second Lagrangian point (L2) of the Sun -- Earth system, yielding a mean distance of a million miles (~ 1.5 million kms) for HSO. From such a distance, HSO is observable as a 17-23 magnitude object moving relatively fast (apparently several arcseconds in a minute) and the actual observed brightness highly depends on the spatial orientation of the spacecraft. This draft describes briefly how observations from this observatory and the subsequent data reductions have been car…
Comparing solar and stellar brightness variations is hampered by the difference in spectral passbands used in observations as well as by the possible difference in the inclination of their rotation axes from the line of sight. We calculate the rotational variability of the Sun as it would be measured in passbands used for stellar observations. In particular, we consider the filter systems used by the CoRoT, $Kepler$, TESS, and $Gaia$ space missions. We also quantify the effect of the inclination of the rotation axis on the solar rotational variability. We employ the Spectral And Total Irradian…
The Vera C. Rubin Observatory Wide-Fast Deep (WFD) sky survey will reach unprecedented surface brightness depths over tens of thousands of square degrees. Surface brightness photometry has traditionally been a challenge. Current algorithms which combine object detection with sky estimation systematically over-subtract the sky, biasing surface brightness measurements at the faint end and destroying or severely compromising low surface brightness light. While it has recently been shown that properly accounting for undetected faint galaxies and the wings of brighter objects can in principle recov…
We present observations of 23 Starlink satellites in the $g'$ bandpass, obtained from the Dominion Astrophysical Observatory's Plaskett 1.8 metre telescope. The targets include a mixture of satellites with and without brightness mitigation measures (i.e., visors). At the time of the observations (16 July 2021), Starlink satellites were sunlight throughout the night, and even with strict elevation and azimuth limits, there were over 800 candidate Starlink arcs. The satellites altogether have a median absolute brightness (550 km) of $\overline{H}_g^{550} =5.3$ mag. Dividing the targets into thos…
The Kilodegree Extremely Little Telescope (KELT) has been surveying more than $70\%$ of the celestial sphere for nearly a decade. While the primary science goal of the survey is the discovery of transiting, large-radii planets around bright host stars, the survey has collected more than $10^6$ images, with a typical cadence between $10-30$ minutes, for more than $4$ million sources with apparent visual magnitudes in the approximate range $7<V<13$. Here we provide a catalog of 52,741 objects showing significant large-amplitude fluctuations likely caused by stellar variability and 62,229 objects…
